Short-Distance Tracers 



Normally the Lagrangian Method is used to describe the tracking of artifi- 

 cial tracers over relatively large distances (e.g. miles). However, several low- 

 inertia tracer methods exist for shorter distances (e.g. less than one meter). 

 Three methods are briefly listed: 



1. Nuclear magnetic resonance . 



2. Photographing the motion of small drops of colored liquid. ^^ 



3. Measure the temperature fluctuations in the wake of a sinusoidally 

 heated fine wire.^^ 



These methods would be more suitable for laboratory or industrial appli- 

 cation (e.g. pipe flow) than for oceanographic field work. Problems in the design 

 of a three-dimensional ocean meter would be large and mainly practical in nature. 

 These methods are not recommended at this time, but should be kept for possible 

 future use. 



MISCELLANEOUS 



Savonius Rotor Meters 



These should never be used in oscillating flow because of poor dynamic 

 response^^ and rectifying action due to the omnidirectional response. ^9 



Thermo-Anemometer Meters 



These types, such as the hot-wire anemometer, relate fluid velocity and 

 the quantity of heat lost by a heated measuring element (thermistors, wires, films). 

 They are inherently suited for high-frequency velocity fluctuations and not for 

 applications requiring long-term stability. Changes in sensitivity due to fouling 

 would probably be serious. Thermo- anemometer meters have no inherent capability 

 for sensing direction and would require shrouds and/or multiple sensor arrays. 

 They are not recommended for the present application. 



40 



